CLASS: X NCERT (CBSE)
PHYSICS
Human Eye and Colourful World
Question 1: The change in focal length of an eye lens to focus the image of objects at varying distances is done by the action of ________.
1. pupil
2. ciliary muscles
3. retina
4. blind spot
Answer: 2
Question 2: Far point of a normal eye is situated at _________.
1. 25 cm
2. infinity
3. 50 cm
4. 400 cm
Answer: 2
Question 3: A long-sighted person cannot see objects nearer to his eye than 50 cm. To enable him to read a book 25 cm away, he should use spectacle lenses whose power in dioptres is ____.
1. -6
2. -4
3. -2
4. + 4
Answer: 4
Question 4: The process by which a beam of white light splits into its constituent colours is known as _________.
1. reflection
2. dispersion
3. divergence
4. convergence
Answer: 2
Question 5: The band of colours obtained due to dispersion is known as ______________.
1. spectrum
2. rainbow
3. image
4. mirage
Answer: 1
Question 6: Power of a lens is expressed in
1. dioptre
2. cm
3. metre
4. millimetre
Answer: 1
Question 7: 1 D is the power of a lens of focal length ______ cm.
1. 100
2. 10
3. 1/100
4. 1/10
Answer: 1
Question 8: Hypermetropia is rectified by using
1. convex lens
2. concave lens
3. cylindrical lens
4. progressive lens
Answer: 1
Question 9: Reciprocal of focal length in metres is known as the ______ of a lens.
1. focus
2. power
3. power of accommodation
4. far point
Answer: 2
Question 10: The power of a convex lens of focal length 50 cm is ______.
1. + 2 D
2. – 2 D
3. 50 D
4. – 5 D
Answer: 1
Question 11: Two lenses having powers +2D and -4D respectively are put together. Power of the combination would be
1. -2 D
2. +2 D
3. -4 D
4. +4 D
Answer: 1
Question 12: The fluid between the retina and the lens is called _______.
1. aqueous humour
2. vitreous humour
3. aqua
4. humus
Answer: 2
Question 13: Two thin lenses of power +5D and -2D are put in contact with each other. Focal length of the combination is
1. +3 m
2. -3 m
3. 0.33 m
4. -0.33 m
Answer: 3
Question 14: The least distance of distinct vision for infants is _________.
1. 15 cm
2. 20 cm
3. 25 cm
4. 5 cm
Answer: 4
Question 15: The focal length of a lens whose power is -1.5 D is _______.
1. -66.66 cm
2. + 1.5 m
3. + 66.66 cm
4. -1.5 m
Answer: 1
